Individual study: Pest control experiments show benefits of complexity at landscape and local scales
Chaplin-Kramer R. & Kremen C. (2012) Pest control experiments show benefits of complexity at landscape and local scales. Ecological Applications, 22, 1936-1948
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Pest regulation: Plant flowers
A replicated site comparison in 2008–2009 in broccoli fields in the Salinas Valley, California, USA, found that cabbage aphids Brevicoryne brassicae were better controlled by natural enemies on complex than on simple farms. Pest regulation: In August, the proportional reduction in aphid densities (PRD) was higher on complex than on simple farms, if farms were surrounded by low amounts of natural habitat (data were reported as the negative log of PRD), but not if surrounded by high amounts of natural habitat. In June, PRD was not significantly different between complex and simple farms. Methods: Eight farms were compared in 2008 and 10 farms were compared in 2009. Flowers for beneficial insects were planted on complex but not on simple farms. Complex and simple farms also differed in field size (1.2–4 vs 6–12 ha) and crop composition (polyculture vs monoculture). Potted broccoli plants were inoculated with 50 aphids each, placed in fields for 12 days, and either caged (to exclude natural enemies) or uncaged. Farms were surrounded by high (>50%) or low (<10%) amounts of natural habitat (0.5–3 km). It was not clear whether these results were a direct effect of planting flowers, field size, or crop composition.